Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About Wipro hiring for Blockchain roles
Wipro is an Indian multinational technology services and consulting company providing IT, cloud, cybersecurity, engineering and data analytics services to enterprises worldwide. Its delivery teams work on application development, quality engineering and data platforms for clients in sectors like banking, healthcare and energy. In India it hires for testing, data analysis, support and development roles through programmes such as Wipro Elite NTH.
For Blockchain roles, this Wipro practice set focuses most on dApp Development (6), Smart Contract Security (5), DeFi, Tokens and NFTs (5), Blockchain Fundamentals (4). It has 17 easy, 11 medium, 2 hard questions, so you can start easy and work up to the harder ones.
Company type
IT services
Headquarters
Bengaluru, India
Main India offices
Bengaluru, Hyderabad, Pune, Chennai, Kolkata
Wipro Blockchain interview process
Online assessment (aptitude + written communication)
Coding test
Technical interview
HR round
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
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A dApp usually has smart contracts on a chain holding core logic and assets; a front-end, often React or Next.js, that connects to the user's wallet; a library such as ethers.js, viem or wagmi to read and write contracts through an RPC provider; an indexer or subgraph for fast queries of history; decentralised storage such as IPFS for files and metadata; and optional back-end services for notifications, relaying or off-chain computation, with oracles bringing external data on-chain.
02
What are the basic Foundry commands to create, build, test and work with a project?
curl -L https://foundry.paradigm.xyz | bash && foundryup
forge init my-dapp # new project with src, test, script
forge install OpenZeppelin/openzeppelin-contracts
forge build # compile
forge test -vvv # run tests with traces
forge coverage # coverage report
forge snapshot # gas snapshot
anvil # local node
cast call ADDR 'count()(uint256)' --rpc-url $RPC
Foundry tests are written in Solidity and run fast; Hardhat is the JavaScript or TypeScript alternative with a large plugin ecosystem.
03
How do you handle a user on the wrong network in your dApp?
The EVM is the sandboxed, deterministic runtime that executes smart contract bytecode on every Ethereum node. It is a stack-based machine with 256-bit words, and each opcode has a gas cost, so every computation is metered and infinite loops are impossible. Because every node must get the same result, contracts cannot access the internet or randomness directly. Many chains and rollups are EVM-compatible, so the same Solidity contracts and tools work across them.
05
A function that distributes rewards loops over all users and is getting too expensive. How do you fix it?
Unbounded loops eventually exceed the block gas limit. Switch to a pull-based accounting model: maintain a global reward-per-token accumulator that grows when rewards are added, and store each user's last checkpoint. Users claim with reward equals balance times (current accumulator minus their checkpoint). This makes distribution O(1) for any number of users. Alternatively, use a Merkle distributor where rewards are computed off-chain and users claim with proofs.
In Proof of Work, miners repeatedly change a nonce and hash the block header until the hash is below a difficulty target. Finding it takes huge computation, but anyone can verify it with one hash. The first miner to succeed broadcasts the block and earns the block reward plus fees. Nodes follow the chain with the most accumulated work. Bitcoin targets a block every ten minutes and adjusts difficulty every 2016 blocks to keep that pace.
IPFS, the InterPlanetary File System, is a peer-to-peer network for storing and sharing files. Instead of locating files by server address, it identifies them by a content identifier (CID) derived from the file's hash, which is content addressing. The same content always has the same CID, and any change gives a new CID, so data cannot be swapped silently. Files must be pinned by a node or pinning service, otherwise they may disappear.
The Merge, completed in September 2022, switched Ethereum from Proof of Work to Proof of Stake by joining the original execution chain with the Beacon Chain, which had been running PoS since December 2020. Mining ended, energy use fell by more than 99.9 percent, and new ETH issuance dropped sharply. Block times became a fixed 12 seconds. Staked ETH withdrawals were enabled later in the Shapella upgrade of April 2023.
Cross-function reentrancy happens when an attacker re-enters a different function that shares state with the one making the external call, so a guard on only one function does not help. Read-only reentrancy happens when a view function, such as a pool's price getter, returns inconsistent state mid-execution, and another protocol reads it during the callback and misprices assets. Mitigate by guarding all state-sharing functions, updating state before calls, and checking a reentrancy lock in view functions other protocols rely on.
10
What are seed phrases and HD wallets (BIP-39, BIP-32, BIP-44)?
BIP-39 encodes random entropy as a 12 or 24 word mnemonic, which is turned into a binary seed. BIP-32 defines hierarchical deterministic wallets that derive a tree of key pairs from that seed. BIP-44 standardises the derivation path, for example m/44'/60'/0'/0/0 for the first Ethereum account. So one backed-up seed phrase can restore unlimited addresses across chains. Whoever knows the phrase controls every derived account, so it must never be stored online.
11
What is a digital signature and what does it guarantee?
A digital signature is a value produced by signing a message hash with a private key. Anyone with the public key can verify it. It guarantees authentication (the holder of the key signed it), integrity (the message was not changed, since any change breaks verification) and non-repudiation (the signer cannot later deny it). In blockchain, every transaction is signed, so nodes accept a transfer only if the signature matches the sending account.
12
How do you keep up with security and cryptography developments in Web3?
I follow a routine. Weekly I read new audit reports and post-mortems of exploits, and I try to reproduce one in Foundry. I track Ethereum Improvement Proposals and upgrade notes, read Solidity release notes, and practise on capture-the-flag platforms such as Ethernaut and Damn Vulnerable DeFi. I also keep a personal notes file of attack patterns. This keeps my knowledge practical rather than just theoretical, and I share summaries with my team.
13
Explain storage, memory, stack and calldata in the EVM.
Storage is persistent key-value data of 32-byte slots per contract; it is the most expensive, and writes to new slots cost about 20,000 gas. Memory is a temporary byte array cleared after each call, cheap but growing in cost quadratically. The stack holds up to 1024 words for opcode operands. Calldata is the read-only input data of the transaction, the cheapest place to read external function arguments from. Choosing the right location is a key gas optimisation.
The mempool is each node's waiting area for valid transactions that have been broadcast but not yet included in a block. Block producers usually pick transactions paying the highest fees or priority tips. Every node has its own mempool, so contents can differ slightly. Because pending transactions are public, bots can watch the mempool and front-run trades, which is why private transaction relays and order-flow auctions are used for sensitive transactions.
15
How does a constant product automated market maker work, and what is impermanent loss?
A constant product AMM holds two tokens with reserves x and y and keeps x times y equal to k. A trader adds one token and removes the other so that k stays constant after fees, which makes price equal to the reserve ratio and rise with trade size. Liquidity providers earn fees, but when prices move, arbitrage rebalances the pool, leaving them worse off than simply holding; that gap is impermanent loss.
16
How do you store an NFT image on IPFS and use it in your contract?
Upload the image to IPFS using a node or a pinning service, which returns a CID. Create a metadata JSON file whose image field is ipfs://<imageCID>, then upload the metadata folder to get a folder CID. Set the contract's base URI to ipfs://<folderCID>/ so tokenURI(5) resolves to the file for token 5. Pin the content with more than one provider, and use a gateway URL only for display in the front-end.
17
How is a blockchain different from a traditional database?
A traditional database is controlled by one administrator who can create, update and delete rows, and trust comes from that owner. A blockchain is shared by many parties, is append-only, and trust comes from cryptography and consensus. The trade-off is performance: a database handles thousands of writes per second with low latency, while a public chain is slower and costlier. Use a blockchain only when several parties who do not fully trust each other must share one record.
18
Design token vesting for team members and early investors.
Use a vesting contract that holds allocated tokens and releases them on a schedule, typically a one-year cliff followed by monthly or linear vesting over two to four years. OpenZeppelin VestingWallet gives linear vesting per beneficiary; add a cliff and an owner-controlled revoke for employees who leave, returning unvested tokens. Make schedules public on-chain for transparency, and avoid admin functions that could release tokens early, as that erodes investor trust.
19
What is a consensus mechanism and why does a blockchain need one?
A consensus mechanism is the set of rules that lets thousands of independent nodes agree on one order of transactions and one current state, even when some nodes are faulty or malicious. Without it, two nodes could accept conflicting transactions and double spending would be possible. Common mechanisms are Proof of Work, Proof of Stake, Proof of Authority and BFT protocols like PBFT, Tendermint and Raft, each trading off decentralisation, speed and fault tolerance.
20
Write a basic ERC-721 NFT contract using OpenZeppelin.
Before 0.8, arithmetic wrapped silently: a uint8 at 255 plus 1 became 0, and 0 minus 1 became the maximum value. Attackers exploited this, for example by making a balance underflow to a huge number or an overflowed multiplication pass a check, as in the 2018 batchOverflow token bug. Developers used the SafeMath library to revert on overflow. Since 0.8 the compiler checks automatically, except inside unchecked blocks and in inline assembly.
A Layer 2 is a network that executes transactions off the main chain and inherits security from it by posting data or proofs back to Layer 1. Ethereum Layer 1 handles only around 15 to 30 transactions per second at higher fees, so L2s batch thousands of transactions into one L1 submission, cutting fees to cents or less. Rollups are the main type. Users bridge assets from L1 to the L2 and can withdraw back.
23
How do you approve and transfer ERC-20 tokens from a script with ethers.js?
Smart contracts cannot call web APIs, so use an oracle. Options include a decentralised oracle network such as Chainlink Functions to fetch from several sports APIs and aggregate, or an optimistic oracle where results are proposed and can be disputed. Settle only after the match result is final, use multiple data sources, add a dispute window for high-value pools, and handle cancelled matches. Avoid a single back-end key posting results, which is a central point of failure.
25
What are front-running and sandwich attacks, and how do you mitigate them?
Pending transactions are public, so bots can copy or outbid them. Front-running is placing a transaction ahead of a victim's, for example buying before a large purchase. A sandwich attack buys before the victim's swap and sells right after, profiting from the price impact. Mitigations include slippage limits and deadlines, commit-reveal schemes, batch auctions, private transaction relays, and design that does not reward ordering, such as using time-weighted prices.
26
Show a contract vulnerable to reentrancy and a fixed version.
With delegatecall, the implementation's code writes to the proxy's storage. If the proxy stores its admin or implementation address in a normal slot, implementation variables can overwrite it, so EIP-1967 uses pseudo-random slots. New implementation versions must only append variables, or use namespaced storage (ERC-7201). Implementations must also disable initialisers in their constructor; otherwise an attacker can initialise the implementation directly, take ownership and, in UUPS, potentially destroy or hijack it.
28
Explain public, private and consortium blockchains.
A public blockchain such as Bitcoin or Ethereum lets anyone read, transact and run a validator. A private blockchain is run by one organisation that controls who joins, useful for internal audit trails. A consortium (permissioned) blockchain is governed by a group of organisations, for example several banks sharing trade-finance data on Hyperledger Fabric. Public chains give maximum decentralisation; permissioned chains give privacy, known identities and higher throughput.
Fiat-backed stablecoins hold cash and short-term government bonds off-chain, one dollar per token, and depend on the issuer's audits and redemptions. Crypto-collateralised stablecoins are minted against overcollateralised crypto in smart contracts, such as vaults requiring 150 percent collateral. Algorithmic stablecoins try to hold the peg with supply rules and incentives; several have collapsed, the most famous in 2022. Choose based on trust model, liquidity, transparency and regulatory status.
Use a specific, sincere answer. For example: I first got interested when I built a small token contract in college and saw that code could hold and move value without a middleman. Since then I have completed Solidity projects, learnt Foundry testing and read audit reports. I like that the field mixes cryptography, distributed systems and finance. I want to grow as a smart contract developer and help build secure, real-world applications such as payments, tokenisation or supply chain.
Tips to crack the Wipro Blockchain interview
Prepare for the essay writing section in the online test by practising short, clear, grammatically correct essays on general topics.
Revise basic coding problems on strings and arrays plus fundamentals of DBMS, operating systems and computer networks.
Learn about Wipro's values, known as the Spirit of Wipro, and its focus areas such as cloud and cybersecurity.
Keep a one-minute story ready for every project on your CV: problem, your part, tools, result.
Practise the hard questions on this page aloud; Wipro interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the Wipro Blockchain interview?
Candidates usually go through 4 stages: Online assessment (aptitude + written communication); Coding test; Technical interview; HR round. The exact rounds change with the role, team, location and your experience, so confirm the process with the recruiter.
Which topics should I prepare for the Wipro Blockchain interview?
This practice set leans on dApp Development (6), Smart Contract Security (5), DeFi, Tokens and NFTs (5), Blockchain Fundamentals (4). Revise those first, then practise explaining one or two of your own projects end to end, because most Wipro interviewers ask you to walk through real work.
Are these the exact questions asked at Wipro?
No. These are curated practice questions that match the skills and difficulty usually tested in it services interviews like Wipro's. They are not a leaked or verified list of past questions.
Where does Wipro hire Blockchain professionals in India?
Wipro has large teams in Bengaluru, Hyderabad, Pune, Chennai, Kolkata. Openings and locations change often, so check the Wipro careers page and filter by city and experience.